I have multiple people in the field filling out a survey, do I need to get each of them an individual login to use the software.
When you say internal survey, do you mean a survey that is only accessible by users in your ArcGIS Online account?
If this is the case, then each user of the survey needs to have their own log in to your ArcGIS Online account, or another ArcGIS Online account the survey is shared with to be within the ArcGIS licensing agreement.
In saying this, it might be worth contacting your account manager at Esri directly because your case could differ to other customers.
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